1. Field of the Invention
The present invention relates to the agricultural machines known as rakes, and more specifically to "V" rakes.
2. Description of the Prior Art
Up to date many types of so-called "V" rakes are known. They are characterised by the fact that they have a frame on which are hinged arms, to which are attached the fingerwheels which have the purpose of raking up the forage.
These arms can thus take on a number of different positions with respect to said frame. In particular, they can be opened to take on the typical "V" shape when working, or they can be closed, that is to say folded together, when manoeuvring and during transport, in order to reduce the working size.
The opening and closing mechanisms on these arms are made up of articulated polygons activated by hydraulic pistons.
The articulations of these polygons are mostly formed by articulated joints capable of allowing rotation, and by slip joints.
These joints, in particular, are commonly made using pieces of square or rectangular cross-section prismatic pipe sliding coaxially along other pipes with a similar cross-section but of a different size.
Normally speaking, these slip joints are reinforced at the points of maximum stress and wear.
The problem resulting from this manufacturing solution is that these slip joints or sleeves, when used in the mechanisms opening and closing the mobile arms of "V" rakes, have a high internal friction level. Because of this internal friction, a high level of force is required to move the slip joints which results in high wear, and there is also the danger of blocking during opening and closing operations if these are carried out while the machine is under stress.
Another problem is that these negative phenomena tend to increase as the machine gets older, until there is a risk of complete blockage of the machine during opening and closing operations, with the consequent risk of breakage of the machine's articulations.